About Chain Letters

(http://www.zyra.org.uk/chainlet.htm)

(http://www.cs.rutgers.edu/~watrous/chain-letters.html)

(http://www.fraudbureau.com/articles/misc/article2.html)

連鎖信與金字塔計劃

(http://www.info.gov.hk/police/pda_c/con-tricks/con8.htm)